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Advisory 012002: PHP remote vulnerabilities
From: security () e-matters de
Date: Wed, 27 Feb 2002 12:30:56 +0100

                           e-matters GmbH
                          www.e-matters.de

                      -= Security  Advisory =-



     Advisory: Multiple Remote Vulnerabilites within PHP's fileupload code
 Release Date: 2002/02/27
Last Modified: 2002/02/27
       Author: Stefan Esser [s.esser () e-matters de]

  Application: PHP v3.10-v3.18, v4.0.1-v4.1.1
     Severity: Several vulnerabilities in PHP's fileupload code allow
               remote compromise
         Risk: Critical
Vendor Status: Patches Released
    Reference: http://security.e-matters.de/advisories/012002.html



Overview:
        
   We found several flaws in the way PHP handles multipart/form-data POST 
   requests. Each of the flaws could allow an attacker to execute arbitrary 
   code on the victim's  system.
 
        
Details:

   PHP supports multipart/form-data POST requests (as described in RFC1867) 
   known as POST fileuploads. Unfourtunately there are several flaws in the
   php_mime_split function that could be used by an attacker to execute
   arbitrary code. During our research we found out that not only PHP4 but
   also older versions from the PHP3 tree are vulnerable.
   
   
   The following is a list of bugs we found:
   
   PHP 3.10-3.18
   
      - broken boundary check    (hard to exploit)
      - arbitrary heap overflow  (easy exploitable)
   
   PHP 4.0.1-4.0.3pl1
   
      - broken boundary check    (hard to exploit)
      - heap off by one          (easy exploitable)
      
   PHP 4.0.2-4.0.5
   
      - 2 broken boundary checks (one very easy and one hard to exploit)
      
   PHP 4.0.6-4.0.7RC2
   
      - broken boundary check    (very easy to exploit)
      
   PHP 4.0.7RC3-4.1.1
   
      - broken boundary check    (hard to exploit)


   Finally I want to mention that most of these vulnerabilities are 
   exploitable only on linux or solaris. But the heap off by one is only
   exploitable on x86 architecture and the arbitrary heap overflow in
   PHP3 is exploitable on most OS and architectures. (This includes *BSD)

   Users running PHP 4.2.0-dev from cvs are not vulnerable to any of the
   described bugs because the fileupload code was completly rewritten for 
   the 4.2.0 branch. 
   

Proof of Concept:

   e-matters is not going to release exploits for any of the discovered
   vulnerabilities to the public. 
   

Vendor Response:

   Because I am part of the php developer team there is not much I can
   write here...

   27th February 2002 - An updated version of php and the patch for
                        these vulnerabilities are now available at:
                        http://www.php.net/downloads.php
                

Recommendation:

   If you are running PHP 4.0.3 or above one way to workaround these 
   bugs is to disable the fileupload support within your php.ini 
   (file_uploads = Off) If you are running php as module keep in mind
   to restart the webserver. Anyway you should better install the 
   fixed or a properly patched version to be safe.
   
   
Sidenotice: 

   This advisory is so short because I don't want to give out more info
   than is needed.
   
   Users running the developer version of php (4.2.0-dev) are not 
   vulnerable to these bugs because the fileupload support was completly
   rewritten for that branch.


GPG-Key:

   http://security.e-matters.de/gpg_key.asc
    
   pub  1024D/75E7AAD6 2002-02-26 e-matters GmbH - Securityteam
   Key fingerprint = 43DD 843C FAB9 832A E5AB  CAEB 81F2 8110 75E7 AAD6


Copyright 2002 Stefan Esser. All rights reserved.




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